<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style>
		
		.left{
			float:left;
		}
		.right{
			float:right;
		}
		.left,.right{
			width:200px;
			background-color:#3F0;
		}
		.middle{
			margin-left:200px;
			margin-right:200px;
			background-color:#C00;
		}

	</style>
</head>
<body>
	<div class="wrap">w
	  <div class="left">left</div>
	  <div class="right">right</div>
	  <div class="middle">middle</div>
	</div>
</body>
</html>